The present invention relates to a brush-equipped motor.
Such a kind of a motor is configured so that, for example, a commutator is provided at a rotor side, that a brush is provided at a stator side, and that this brush is slidably contacted with the commutator to thereby electrically conduct an external power supply circuit, which is connected to the brush, to a driving coil that is connected to the commutator and wound around the rotor. Thus, electric current is periodically supplied to the driving coil. Consequently, magnetic field action between such a coil and a field magnet drives the rotor to rotate.
Meanwhile, in the case of such a kind of a motor, when frequently repeating start/stop, sparks generated between the commutator and the brush at that time cause the brush to wear out. Then, such a kind of a motor causes problems in that the commutator and the brush are brought into a non-contact state, and that thus the motor cannot be driven. In such a case, the conventional brush-equipped motor is not configured so that only a worn-out brush can be exchanged. Eventually, a manufacturer needs to collect products and to replace each of the motors itself with a new one. That is, the conventional brush-equipped motor has a drawback that the life thereof ends when the brush wears out.
The present invention is accomplished in view of the aforementioned circumstances. An object of the present invention is to provide a brush-equipped motor enabled to be used for a long time without performing operations, such as replacement of a motor, and without interruption even when the brush wears out.
To accomplish the above object of the present invention, according to a first aspect of the present invention, there is provided a brush-equipped motor, comprising: a rotor; a commutator provided at a side of the rotor; a stator; brushes provided at a side of the stator; reserve-brushes provided at the side of the stator; and a brush exchanging mechanism having projections, wherein the brush exchanging mechanism is changed the brush-equipped motor from a first state in which the brushes are in contact with the commutator and the reserve-brushes are detached from the commutator by the projections, to a second state in which the brushes are detached from the commutator by the projections and the reserve-brushes are in contact with the commutator.
According to a second aspect of the present invention, there is provided a brush-equipped motor as set forth in the first aspect of the present invention, wherein each of the brushes and the reserve-brushes has: a brush body slidably contacted with the commutator, and an elastic piece attached to the brush body and arranged in a circumferential direction of the commutator, wherein the brush exchanging mechanism has a rotary body adapted to perform a turning operation concentrically with the rotor; and the projections have a plurality of projections being in contact with each of the elastic pieces of the brushes and the reserve-brushes and provided on the rotary body, wherein in the first state, by turning the rotary body, the elastic pieces of the reserve-brushes contact with the projections to thereby prevent the brush bodies thereof from being in contact with the commutator, and in the second state, the elastic pieces of the brushes contact with the projections to thereby prevent the brush bodies thereof from being in contact with the commutator.
According to a third aspect of the present invention, there is provided a brush-equipped motor as set forth in the second aspect of the present invention, wherein in the first state, the elastic pieces of the brushes contact with the projections to thereby regulate an amount of displacement of each of the brush bodies to the commutator side, which is caused owing to wear of the brush bodies thereof, and in the second state, the elastic pieces of the reserve-brushes contact with the projections to thereby regulate an amount of displacement of each of the brush bodies to the commutator side, which is caused owing to wear of the brush bodies thereof.
In the present invention, it is preferable that a brush-equipped motor as set forth in the first aspect, wherein each of the projections have a cam shape having a surface contacting with the brushes and the reserve brushes and constituted by a curved part having a gentle gradient.
It is also preferable that a method of exchanging brushes of a brush-equipped motor, method of exchanging brushes of a brush-equipped motor, comprising steps of: preparing brushes provided at a side of a stator of the brush-equipped motor, reserve-brushed provided at the side of the stator and a commutator provided at a side of a rotor of the brush-equipped motor; changing a state of the motor from a first state, in which each of the brushes are in contact with the commutator, and the reserve-brushes are detached from the commutator by projections, to a second state, in which the projections are moved, and the brushes are detached from the commutator by the projections, and the reserve-brushes are in contact with the commutator.
With a configuration of the first aspect of the present invention, first, the brush-equipped motor is put into a first state in which the reserve-brushes are detached from the commutator, and in which only the brushes are in contact with the commutator. In the case that the motor is used in this state for a long term, actually, the brushes wear out owing to slidably contact between the commutator and each of the brushes. Thus, the brush exchanging mechanism changes the state of the brush-equipped motor to a second state in which the brushes are detached from the commutator, and in which the reserve-brushes are in contact with the commutator. Thus, the worn-out brushes can be exchanged with the reserve-brushes. Consequently, the motor can be used still more until the reserve-brushes wear. Therefore, such a simple operation enables the continuing use of the motor can be used for a long time being longer than the time, during which the aforementioned conventional brush-equipped motor can be used, without performing an operation of exchanging the motor.
With a configuration of the second aspect of the present invention, as the rotary body turns, the projections provided on the rotary body abut the elastic pieces of the reserve-brushes to thereby prevent the brush bodies thereof from being in contact with the commutator. Consequently, the motor is brought into the first state in which the brushes come into contact with the commutator and in which the reserve-brushes are detached from the commutator. When the rotary body is turned during such a state, the projections of the rotary body contact with the elastic pieces of the brushes this time to thereby prevent the brush bodies thereof from coming in contact with the commutator. That is, for example, the brushes are prevented from being destroyed by a shock that is caused by abruptly releasing the elastic pieces. Consequently, the state of the motor is changed into a second state in which the brushes are detached from the commutator, and in which the reserve-brushes are in contact with the commutator. Hence, the brushes can be easily exchanged to the reserve-brushes only by performing a simple turning operation of the rotary body.
In the case that the motor is used for a long time, the commutator is sometimes damaged by, for example, brushes, which become difficult to abrade and harder than the brushes before wearing-out, and by exposed elastic pieces. In such a case, it is insufficient to exchange only the brushes. Eventually, the motor itself should be replaced with a new one. Thus, according to the third aspect of the present invention, in the first state, the projections of the rotary body are made to contact with the elastic pieces of the brushes, which are currently used. Consequently, an amount of displacement thereof to the commutator, which is caused by the wear-out of the brush bodies, is regulated. Thus, even in the case that the motor is used for a long term, the brush bodies are prevented from coming in contact with the commutator before excessively worn out. Consequently, the commutator can be prevented from being damaged.